Reject offers with some fields present but empty (#3175)

Offers or invoices where the fields `offer_chains`, `offer_paths`, `invoice_paths`, `invoice_blindedpay` are present but empty are considered invalid.
While the spec does not necessarily rejects them explicitly, they can't be paid.

Author: thomash-acinq

eclair-core/src/main/scala/fr/acinq/eclair/payment/Bolt12Invoice.scala

@@ -127,7 +127,7 @@ object Bolt12Invoice {
       _ -> ()
     )
     if (records.get[InvoiceAmount].isEmpty) return Left(MissingRequiredTlv(UInt64(170)))
-    if (records.get[InvoicePaths].forall(_.paths.isEmpty)) return Left(MissingRequiredTlv(UInt64(160)))
+    if (records.get[InvoicePaths].isEmpty) return Left(MissingRequiredTlv(UInt64(160)))
     if (records.get[InvoiceBlindedPay].map(_.paymentInfo.length) != records.get[InvoicePaths].map(_.paths.length)) return Left(MissingRequiredTlv(UInt64(162)))
     if (records.get[InvoiceNodeId].isEmpty) return Left(MissingRequiredTlv(UInt64(176)))
     if (records.get[InvoiceCreatedAt].isEmpty) return Left(MissingRequiredTlv(UInt64(164)))

eclair-core/src/main/scala/fr/acinq/eclair/wire/protocol/CommonCodecs.scala

@@ -205,4 +205,12 @@ object CommonCodecs {
     (bits: BitVector) => Attempt.fromTry(Try(codec.decode(bits))).flatten
   )
 
+  def nonEmptyList[A](codec: Codec[A], name: String): Codec[Seq[A]] =
+    list(codec).narrow(l => {
+      if (l.nonEmpty) {
+        Attempt.successful(l.toSeq)
+      } else {
+        Attempt.failure(Err(s"$name must not be empty"))
+      }
+    }, _.toList)
 }

eclair-core/src/main/scala/fr/acinq/eclair/wire/protocol/OfferCodecs.scala

@@ -16,7 +16,6 @@
 
 package fr.acinq.eclair.wire.protocol
 
-import fr.acinq.bitcoin.scalacompat.BlockHash
 import fr.acinq.bitcoin.scalacompat.Crypto.PublicKey
 import fr.acinq.eclair.crypto.Sphinx.RouteBlinding.{BlindedHop, BlindedRoute}
 import fr.acinq.eclair.wire.protocol.CommonCodecs._
@@ -30,7 +29,7 @@ import java.util.Currency
 import scala.util.Try
 
 object OfferCodecs {
-  private val offerChains: Codec[OfferChains] = tlvField(list(blockHash).xmap[Seq[BlockHash]](_.toSeq, _.toList))
+  private val offerChains: Codec[OfferChains] = tlvField(nonEmptyList(blockHash, "offer_chains"))
 
   private val offerMetadata: Codec[OfferMetadata] = tlvField(bytes)
 
@@ -76,7 +75,7 @@ object OfferCodecs {
       ("firstPathKey" | publicKey) ::
       ("path" | blindedNodesCodec)).as[BlindedRoute]
 
-  private val offerPaths: Codec[OfferPaths] = tlvField(list(blindedRouteCodec).xmap[Seq[BlindedRoute]](_.toSeq, _.toList))
+  private val offerPaths: Codec[OfferPaths] = tlvField(nonEmptyList(blindedRouteCodec, "offer_paths"))
 
   private val offerIssuer: Codec[OfferIssuer] = tlvField(utf8)
 
@@ -138,7 +137,7 @@ object OfferCodecs {
     .typecase(UInt64(240), signature)
   ).complete)
 
-  private val invoicePaths: Codec[InvoicePaths] = tlvField(list(blindedRouteCodec).xmap[Seq[BlindedRoute]](_.toSeq, _.toList))
+  private val invoicePaths: Codec[InvoicePaths] = tlvField(nonEmptyList(blindedRouteCodec, "invoice_paths"))
 
   val paymentInfo: Codec[PaymentInfo] =
     (("fee_base_msat" | millisatoshi32) ::
@@ -148,7 +147,7 @@ object OfferCodecs {
       ("htlc_maximum_msat" | millisatoshi) ::
       ("features" | variableSizeBytes(uint16, bytes))).as[PaymentInfo]
 
-  private val invoiceBlindedPay: Codec[InvoiceBlindedPay] = tlvField(list(paymentInfo).xmap[Seq[PaymentInfo]](_.toSeq, _.toList))
+  private val invoiceBlindedPay: Codec[InvoiceBlindedPay] = tlvField(nonEmptyList(paymentInfo, "invoice_blindedpay"))
 
   private val invoiceCreatedAt: Codec[InvoiceCreatedAt] = tlvField(tu64overflow.as[TimestampSecond])
 

eclair-core/src/main/scala/fr/acinq/eclair/wire/protocol/OfferTypes.scala

@@ -308,7 +308,7 @@ object OfferTypes {
 
     def validate(records: TlvStream[OfferTlv]): Either[InvalidTlvPayload, Offer] = {
       if (records.get[OfferDescription].isEmpty && records.get[OfferAmount].nonEmpty) return Left(MissingRequiredTlv(UInt64(10)))
-      if (records.get[OfferNodeId].isEmpty && records.get[OfferPaths].forall(_.paths.isEmpty)) return Left(MissingRequiredTlv(UInt64(22)))
+      if (records.get[OfferNodeId].isEmpty && records.get[OfferPaths].isEmpty) return Left(MissingRequiredTlv(UInt64(22)))
       if (records.get[OfferCurrency].nonEmpty && records.get[OfferAmount].isEmpty) return Left(MissingRequiredTlv(UInt64(8)))
       if (records.unknown.exists(!isOfferTlv(_))) return Left(ForbiddenTlv(records.unknown.find(!isOfferTlv(_)).get.tag))
       Right(Offer(records))

eclair-core/src/test/scala/fr/acinq/eclair/payment/Bolt12InvoiceSpec.scala

@@ -383,4 +383,9 @@ class Bolt12InvoiceSpec extends AnyFunSuite {
     assert(invoice.checkSignature())
     assert(invoice.amount == 1000000000.msat)
   }
+
+  test("invoice paths is set but and empty") {
+    val invoiceWithEmptyPaths = "lni1qqx2n6mw2fh2ckwdnwylkgqzypp5jl7hlqnf2ugg7j3slkwwcwht57vhyzzwjr4dq84rxzgqqqqqqzqrq83yqzscd9h8vmmfvdjjqamfw35zqmtpdeujqenfv4kxgucvqqfq2ctvd93k293pq0zxw03kpc8tc2vv3kfdne0kntqhq8p70wtdncwq2zngaqp529mmc5pqgdyhl4lcy62hzz855v8annkr46a8n9eqsn5satgpagesjqqqqqq9yqcpufq9vqfetqssyj5djm6dz0zzr8eprw9gu762k75f3lgm96gzwn994peh48k6xalctyr5jfmdyppx7cneqvqsyqaqqz3qpfqyv2sqd04xqg8pp2pq2x236nzneyzqxhct9y7unhcupeukwgf5xzhq0f0nuy6v6vej2dq65qcpufq2cysyqqzpy02klqrqqz8t8twx39z77cq6uq9syypugee7xc8qa0pf3jxe9k0976dvzuqu8eaedk0pcpg2dr5qx3gh008sgrn58w7cg2qhcunaapk9j6patmtda7nhqhzvwv6hflxygyrrglpqka8l6zfhfhprxazkufcn88rl07yxfp5mvjl70etp2pzdkhud3ekul5qnjq46hg"
+    assert(Bolt12Invoice.fromString(invoiceWithEmptyPaths).isFailure)
+  }
 }

eclair-core/src/test/scala/fr/acinq/eclair/wire/protocol/OfferTypesSpec.scala

@@ -350,4 +350,14 @@ class OfferTypesSpec extends AnyFunSuite {
     assert(OfferCodecs.offerCurrency.decode(encode("XAU")).isFailure)
     assert(OfferCodecs.offerCurrency.decode(hex"ffffff".bits).isFailure)
   }
+
+  test("empty fields") {
+    val invalidOffers = Seq(
+      Offer(TlvStream(OfferPaths(Nil))),
+      Offer(TlvStream(OfferNodeId(randomKey().publicKey), OfferChains(Nil))),
+    )
+    for (invalidOffer <- invalidOffers) {
+      assert(Offer.decode(invalidOffer.toString).isFailure)
+    }
+  }
 }